Acoustic wave device with anti-reflection layer

ABSTRACT

An acoustic wave device is disclosed. The acoustic wave device includes a piezoelectric layer, an interdigital transducer electrode positioned over the piezoelectric layer, and an anti-refection layer over a conductive layer of the interdigital transducer electrode. The conductive layer can include aluminum, for example. The anti-reflection layer can include silicon. The anti-reflection layer can be free from a material of the interdigital transducer electrode. The acoustic wave device can further include a temperature compensation layer positioned over the anti-reflection layer in certain embodiments.

CROSS REFERENCE TO PRIORITY APPLICATION

This application claims the benefit of priority of U.S. ProvisionalPatent Application No. 62/806,560, filed Feb. 15, 2019 and titled“ACOUSTIC WAVE RESONATOR WITH ANTI-REFLECTION LAYER,” the disclosure ofwhich is hereby incorporated by reference in its entirety herein.

BACKGROUND Technical Field

Embodiments of this disclosure relate to acoustic wave devices.

Description of Related Technology

Acoustic wave filters can be implemented in radio frequency electronicsystems. For instance, filters in a radio frequency front end of amobile phone can include acoustic wave filters. An acoustic wave filtercan filter a radio frequency signal. An acoustic wave filter can be aband pass filter. A plurality of acoustic wave filters can be arrangedas a multiplexer. For example, two acoustic wave filters can be arrangedas a duplexer.

An acoustic wave filter can include a plurality of resonators arrangedto filter a radio frequency signal. Example acoustic wave filtersinclude surface acoustic wave (SAW) filters and bulk acoustic wave (BAW)filters. A surface acoustic wave resonator can include an interdigitaltransductor electrode on a piezoelectric substrate. The surface acousticwave resonator can generate a surface acoustic wave on a surface of thepiezoelectric layer on which the interdigital transductor electrode isdisposed.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

In one aspect, an acoustic wave device is disclosed. The acoustic wavedevice can include a piezoelectric layer, and an interdigital transducerelectrode positioned over the piezoelectric layer. The interdigitaltransducer electrode includes a conductive layer. The acoustic wavedevice can also include an anti-reflection layer positioned over theconductive layer. The anti-reflection layer includes silicon. Theacoustic wave device can further include a temperature compensationlayer over the anti-reflection layer.

In an embodiment, the anti-reflection layer is a silicon oxynitridelayer. The silicon oxynitride layer can have a thickness in a range from100 nanometers to 120 nanometers.

In an embodiment, the anti-reflection layer is an amorphous siliconlayer. The amorphous silicon layer can have a thickness in a range from5 nanometers to 15 nanometers.

In an embodiment, the anti-reflection layer includes a material and hasa thickness that together cause reflectivity of the acoustic wave deviceto be less than or equal to 0.2 for light having a wavelength of 365nanometers. The anti-reflection layer contributes to less than 2 percentof wiring resistance of the acoustic wave device.

In an embodiment, the conductive layer is in physical contact with theanti-reflection layer.

In an embodiment, the interdigital transducer includes a metal layerpositioned between the conductive layer and the piezoelectric layer.

In an embodiment, the acoustic wave device further including a substratelayer. The piezoelectric layer can be on the substrate layer.

In an embodiment, an acoustic wave filter includes acoustic wave devicesarranged to filter a radio frequency signal. The acoustic wave devicesinclude the acoustic wave device. A front end module can include theacoustic wave filter, additional circuitry, and a package enclosing theacoustic wave filter and the additional circuitry. The additionalcircuitry can include a multi-throw radio frequency switch. Theadditional circuitry can include a power amplifier. The acoustic wavefilter can be included in a duplexer. A wireless communication devicecan include an antenna and the acoustic wave filter. The acoustic wavefilter can be arranged to filter a radio frequency signal associatedwith the antenna.

In an embodiment, the conductive layer is an aluminum layer. Theconductive layer can have a reflectivity of at least 0.5 for lighthaving a wavelength of 365 nanometers.

The acoustic wave device can be an acoustic wave resonator. The acousticwave resonator can be a surface acoustic wave resonator.

In one aspect, an acoustic wave device is disclosed. The acoustic wavedevice can include a piezoelectric layer, a interdigital transducerelectrode positioned over the piezoelectric layer, and ananti-reflection layer over the interdigital transducer electrode. Theinterdigital transducer electrode can include a first interdigitaltransducer electrode finger extending from a first bus bar and a secondinterdigital transducer finger extending from a second bus bar. Thefirst interdigital transducer electrode finger and the secondinterdigital transducer electrode finger can be spaced apart from eachother by a gap. The anti-reflection layer can include silicon. Theanti-reflection layer can be free from material of the interdigitaltransducer electrode. The piezoelectric layer can be free from theanti-reflection layer under the gap.

The acoustic wave device further includes a temperature compensationlayer over the anti-reflection layer.

In an embodiment, the anti-reflection layer is an amorphous siliconlayer. the amorphous silicon layer can have a thickness in a range from5 nanometers to 15 nanometers.

The acoustic wave device of claim 8 wherein the anti-reflection layer isa silicon oxynitride layer. The silicon oxide layer can have a thicknessin a range from 100 nanometers to 120 nanometers.

In an embodiment, the interdigital transducer electrode includes analuminum layer. The anti-reflection layer can be in physical contactwith the aluminum layer. The anti-reflection layer can have areflectivity of 0.2 or less for light having a wavelength of 365nanometers.

In an embodiment the anti-reflection layer has a reflectivity range from0.1 to 0.2 at the wavelength of 365 nanometers.

In an embodiment, a line width distribution of the interdigitaltransducer electrode is 2% of the line width or less.

In an embodiment, the acoustic wave device further includes a supportsubstrate. The piezoelectric layer can be over the support substrate.The support substrate can have a higher impedance than the piezoelectriclayer.

The acoustic wave device can be configured to generate a surfaceacoustic wave.

In one aspect, a method of manufacturing an acoustic wave device isdisclosed, the method can include providing an acoustic wave devicestructure with one or more interdigital transducer electrode layers on apiezoelectric layer. The one or more interdigital transducer electrodelayers including a conductive layer. The method can also include formingan anti-reflection layer over the conductive layer. The anti-reflectionlayer includes silicon. The method further includes performing aphotolithography processes to pattern an interdigital transducerelectrode from one or more interdigital transducer electrode layers. Theanti-reflection layer reduces reflection from the conductive layerduring the photolithography process.

In an embodiment, the conductive layer includes aluminum.

In an embodiment, the anti-reflection layer is a silicon oxynitridelayer.

In an embodiment, the anti-reflection layer is an amorphous siliconlayer.

In an embodiment, the anti-reflection layer has a reflectivity of 0.2 orless for light having a wavelength of 365 nanometers.

In an embodiment, the conductive layer has a reflectivity of at least0.5 for light having a wavelength of 365 nanometers.

In an embodiment, the method further includes forming a temperaturecompensation layer over the anti-reflection layer.

In an embodiment, the anti-reflection material remains distinct from thealuminum layer after a heating process.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the innovations have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment. Thus, theinnovations may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIG. 1A illustrates a cross section of a surface acoustic wave (SAW)resonator structure at a stage of a manufacturing process.

FIG. 1B illustrates a cross section of a surface acoustic wave resonatorformed from the surface acoustic wave resonator structure illustrated inFIG. 1A.

FIG. 2A illustrates a cross section of a SAW resonator structure at astage of a manufacturing process according to an embodiment.

FIG. 2B illustrates a cross section of a SAW resonator formed from theSAW resonator structure illustrated in FIG. 2A according to anembodiment.

FIG. 3A is a graph showing a reference wiring resistance measurement anda wiring resistance measurement of the SAW resonator illustrated in FIG.1B.

FIG. 3B is a graph showing a reference wiring resistance measurement anda wiring resistance measurement of the SAW resonator illustrated in FIG.2B.

FIG. 4A is a graph showing ellipsometer measurement results ofreflectivity of an epoxy resin layer, a silicon oxynitride (SiON) layer,and an amorphous silicon (a-Si) layer at a wavelength of 365 nanometers(nm).

FIG. 4B is a table that includes the lowest reflectivity values andcorresponding thicknesses from FIG. 4A for the a-Si layer and the SiONlayer.

FIG. 5A is a graph of measurement results of line widths for differentresist thicknesses of a resist film of a SAW resonator without ananti-reflection layer.

FIG. 5B is a graph of measurement results of line widths for differentresist thicknesses of a resist film of a SAW resonator structure withepoxy resin over an interdigital transducer (IDT) electrode.

FIG. 5C is a graph of measurement results of line widths for differentresist thicknesses of a resist film of a SAW resonator structure with ananti-reflection layer over an IDT electrode according to an embodiment.

FIG. 5D is a graph of measurement results of line widths for differentresist thicknesses of a resist film of a SAW resonator structure with ananti-reflection layer over an IDT electrode according to anotherembodiment.

FIG. 6 is a graph of swing curves of data points at the bottom sides ofthe measurement results illustrated in FIGS. 5A-5D.

FIG. 7 illustrates a cross section of a SAW resonator according to anembodiment.

FIG. 8A illustrates a cross section of a SAW resonator according toanother embodiment.

FIG. 8B illustrates a cross section of a SAW resonator according toanother embodiment.

FIG. 8C illustrates another cross section of the SAW resonatorillustrated in FIG. 8B.

FIG. 9A illustrates a cross section of a Lamb wave device according toan embodiment.

FIG. 9B illustrates a cross section of a Lamb wave device according toanother embodiment.

FIG. 10A is a schematic diagram of a transmit filter that includes asurface acoustic wave resonator according to an embodiment.

FIG. 10B is a schematic diagram of a receive filter that includes asurface acoustic wave resonator according to an embodiment.

FIG. 11 is a schematic diagram of a radio frequency module that includesa surface acoustic wave component according to an embodiment.

FIG. 12 is a schematic diagram of a radio frequency module that includesduplexers with surface acoustic wave resonators according to anembodiment.

FIG. 13A is a schematic block diagram of a module that includes a poweramplifier, a radio frequency switch, and duplexers that include one ormore surface acoustic wave resonators with an anti-reflection layeraccording to an embodiment.

FIG. 13B is a schematic block diagram of a module that includes filters,a radio frequency switch, and a low noise amplifier according to anembodiment.

FIG. 14 is a schematic block diagram of a module that includes anantenna switch and duplexers that include one or more surface acousticwave resonators with an anti-reflection layer according to anembodiment.

FIG. 15A is a schematic block diagram of a wireless communication devicethat includes a filter in accordance with one or more embodiments.

FIG. 15B is a schematic block diagram of another wireless communicationdevice that includes a filter in accordance with one or moreembodiments.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following description of certain embodiments presents variousdescriptions of specific embodiments. However, the innovations describedherein can be embodied in a multitude of different ways, for example, asdefined and covered by the claims. In this description, reference ismade to the drawings where like reference numerals can indicateidentical or functionally similar elements. It will be understood thatelements illustrated in the figures are not necessarily drawn to scale.Moreover, it will be understood that certain embodiments can includemore elements than illustrated in a drawing and/or a subset of theelements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

Acoustic wave filters can filter radio frequency (RF) signals in avariety of applications, such as in an RF front end of a mobile phone.An acoustic wave filter can be implemented with surface acoustic wave(SAW) devices. The SAW devices include SAW resonators, SAW delay lines,and multi-mode SAW (MMS) filters (e.g., double mode SAW (DMS) filters).

A manufacturing process for a SAW device can include a photolithographyprocess. In certain photolithography processes, some undesirable effectscan occur. For example, light used in the photolithography process canreflect back, which can cause standing waves and/or swing curves. ForSAW resonators that include an interdigital transducer (IDT) electrodewith a relatively high reflectivity material, such as an aluminum IDTelectrode, reflection from the IDT electrode is relatively high.Reflection from aluminum IDT electrode layers has presented technicalchallenges in manufacturing IDT electrode patterns with certain linewidths in a photolithography process.

One approach to eliminate and/or mitigate such undesirable effects is toinclude an anti-reflection material over the aluminum IDT electrodelayer. An anti-reflection epoxy resin film can suppress the reflectivityof an aluminum layer. Fixing properties of an epoxy resinanti-reflection film can involve a heating process. However, in such aheating process, the aluminum IDT electrode layer can react with theanti-reflection film to form a compound layer with carbon and aluminum.The thickness of the compound layer can be about 10 nanometers (nm) to20 nm. This thickness can be about 10% to 15% of the thickness of thealuminum IDT electrode. The compound layer can be sparse and a wiringresistance value measured using a resistance wire test (also referred toas a wiring resistance measurement) with this structure can increaseabout 10% compared to a similar structure without an anti-reflectionresin film. The surface of an aluminum IDT electrode with the compoundfilm can be rough. The compound film can contribute to filter lossand/or larger frequency distribution due to the variable thickness ofthe compound layer with aluminum and resin throughout a wafer.

Aspects of this disclosure relate to an anti-reflection film over an IDTelectrode layer of an acoustic wave device. For example, a SAW resonatorcan include a piezoelectric layer, an IDT electrode over thepiezoelectric layer, and an anti-reflection layer over the IDTelectrode. The anti-reflection layer can include silicon. For example,the anti-reflection layer can be a silicon oxynitride layer or anamorphous silicon layer. Anti-reflection layers disclosed herein can befree from material of an IDT electrode layer in contact with theanti-reflection layer. With such an anti-reflection layer, the wiringresistance value can be substantially the same as a similar structurewithout an anti-reflection layer. The anti-reflection layer can have athickness that causes the reflectivity to satisfy a threshold. Withanti-reflection layers disclosed herein, IDT electrodes of acoustic waveresonators can be patterned with line widths in a range from 0.25micrometers (μm) to 0.4 μm in a photolithography process withoutsignificant electrical degradation in filters that include such acousticwave resonators.

Although embodiments may be discussed with reference to SAW resonators,any suitable principles and advantages discussed herein can be appliedto any suitable SAW device and/or any other suitable acoustic wavedevice. Embodiments will now be discussed with reference to drawings.Any suitable combination of features of the embodiments disclosed hereincan be implemented together with each other.

FIG. 1A illustrates a cross section of a surface acoustic wave resonatorstructure at a stage of a manufacturing process. The manufacturingprocess may include a photolithography process. The illustrated SAWresonator structure in FIG. 1A includes a piezoelectric layer 10, aninterdigital transducer (IDT) electrode 12 over the piezoelectric layer10, an anti-reflection epoxy resin film 14 over the IDT electrode 12,and a resist film 16 over the epoxy resin film 14. The IDT electrode 12has an upper surface 12 a in contact with the epoxy resin film 14. Theepoxy resin film 14 is subjected to a heat processing to fix itsproperties in another stage in the manufacturing process. The epoxyresin film 14 is heated prior to removing the resist film 16. The resistfilm 16 gets removed later at a later stage in the manufacturingprocess. For example, the manufacturing process can include: (1)depositing an IDT electrode material layer on the piezoelectric layer10; (2) coating the anti-reflection epoxy resin film 14 on the IDTelectrode material layer; (3) coating the resist film 16 on theanti-reflection epoxy resin film 14; (4) patterning the resist film 16;(5) etching the IDT electrode material layer to form the IDT electrode12; and (6) removing the resist film 16. The anti-reflection epoxy resinfilm 14 can mitigate and/or eliminate back reflection of light from theIDT electrode 12 during the photolithography process. As discussedbelow, this reduction of a reflectivity of the IDT electrode 12 can makea line width range smaller.

FIG. 1B illustrates a cross section of a surface acoustic wave resonator1 formed using the surface acoustic wave resonator structure illustratedin FIG. 1A. The illustrated SAW resonator 1 includes the piezoelectriclayer 10, the IDT electrode 12 over the piezoelectric layer 10, acompound layer 14′ over the IDT electrode 12, and a temperaturecompensation layer 18 over the compound layer 14′.

The piezoelectric layer 10 may include any suitable piezoelectricmaterial, such as a lithium niobate (LN) layer or a lithium tantalate(LT) layer. A thickness tl of the piezoelectric layer 10 can be selectedbased on a wavelength λ or L of a surface acoustic wave generated by thesurface acoustic wave resonator 1 in certain applications. The IDTelectrode 12 has a pitch that sets the wavelength λ or L of the surfaceacoustic wave resonator 1.

The IDT electrode 12 can be an aluminum (Al) IDT electrode. The IDTelectrode 12 has a thickness t2. In some embodiments, the thickness t2of the IDT electrode 12 can be about 0.05 L. For example, when thewavelength L is 4 μm, the thickness t2 can be 200 nm.

The compound layer 14′ is formed when the epoxy resin film 14 is heatedand/or the resist film 16 is heated. Carbon included in the resist film16 can react with a material (e.g., aluminum) of the IDT electrode 12when heated, forming a compound that includes the material (e.g.,aluminum) and carbon. Due to this reaction, relative heights of an uppersurface 14a′ of the compound layer 14′ in FIG. 1B and an upper surface12 a of the IDT electrode in FIG. 1A can be approximately the same. Thecompound layer 14′ has a thickness t3. The thickness t3 may vary alongits width. The thickness t3 of the compound layer 14′ may depend atleast on a thickness of the epoxy resin layer 14 and/or a duration ofthe heat processing. The thickness t3 of the compound layer 14′ can be,for example, in a range from 10 nm to 20 nm. The thickness t3 of thecompound layer 14′ can be, for example, in a range from 10% to 15% ofthickness t2 of the IDT electrode 12.

A final thickness t2′ of the IDT electrode 12 may be different from theoriginal IDT electrode thickness t2. For example, the final thicknesst2′ of the IDT electrode 12 can be approximately the thickness t2 of theoriginal thickness minus the thickness t3 of the compound layer 14′. Incertain embodiments, the final thickness t2′ can be about 180 nm.However, the IDT electrode 12 may be designed to have a thicker originalthickness t2 such that the final thickness t2′ after the formation ofthe compound layer 14′ can be about 200 nm or about 0.05 L.

The temperature compensation layer 18 can include any suitable material.For example, the temperature compensation layer 18 can be a silicondioxide (SiO₂) layer. The temperature compensation layer 18 can bringthe temperature coefficient of frequency (TCF) of the SAW resonator 1closer to zero relative to a similar SAW resonator without thetemperature compensation layer 18. The temperature compensation layer 18has a thickness t4.

FIG. 2A illustrates a cross section of a surface acoustic wave resonatorstructure at a stage of a manufacturing process according to anembodiment. The manufacturing process can include a photolithographyprocess. The illustrated SAW resonator structure of FIG. 2A includes apiezoelectric layer 10, an interdigital transducer (IDT) electrode 12over the piezoelectric layer 10, an anti-reflection layer 20 over theIDT electrode 12, and a resist film 16 over the anti-reflection layer20. The resist film 16 can be removed at a later stage in themanufacturing process. For example, the manufacturing process caninclude: (1) depositing an IDT electrode material layer on thepiezoelectric layer 10; (2) forming the anti-reflection layer 20 on theIDT electrode material layer; (3) coating the resist film 16 on theanti-reflection layer 20; (4) patterning the resist film 16; (5) etchingthe IDT electrode material layer to form the IDT electrode 12; and (6)removing the resist film 16.

The anti-reflection layer 20 can include silicon. For example, theanti-reflection layer 20 can be silicon (Si), silicon oxynitride (SiON),amorphous silicon (a-Si), silicon dioxide (SiO₂), or another suitablesilicon compound. The anti-reflection layer 20 can be a material that issimilar to silicon dioxide. In certain instances, the anti-reflectionlayer 20 can include a non-silicon material that sufficiently mitigatesback reflection in a photolithography process and does not react (e.g.,does not form a compound) with the IDT electrode 12. In certainapplications, the anti-reflection material can be any suitable materialhaving a reflectivity of 0.3 or less for light having a wavelength of365 nm. According to some such applications, the anti-reflectionmaterial can be any suitable material having a reflectivity of 0.2 orless for light having a wavelength of 365 nm. For example, thereflectivity can be in between 0.01 to 0.2, in some embodiments. In someembodiments, the anti-reflection layer 20 does not include carbon.

FIG. 2B illustrates a cross section of a surface acoustic wave resonator2 formed using the surface acoustic wave resonator structure illustratedin FIG. 2A according to an embodiment. The SAW resonator 2 and other SAWresonators with a similar temperature compensation layer can be referredto as a temperature compensated SAW (TC-SAW) resonator.

The illustrated SAW resonator 2 includes the piezoelectric layer 10, theIDT electrode 12 over the piezoelectric layer 10, the anti-reflectionlayer 20 over the IDT electrode 12, and a temperature compensation layer18 over the anti-reflection layer 20. The SAW resonator 2 illustrated inFIG. 2B includes some generally similar features to the SAW resonator 1illustrated in FIG. 1B. However, unlike the SAW resonator 1, the SAWresonator 2 does not include the compound layer 14′ and includes theanti-reflection layer 20. Unlike the anti-reflection epoxy resin film 14of FIG. 1A, the anti-reflection layer 20 does not react with the IDTelectrode 12. Accordingly, the anti-reflection layer 20 is distinct fromthe material of the IDT electrode 12. The anti-reflection layer 20 isfree from material of the IDT electrode 12. In some embodiments, thechemical properties of the anti-reflection layer 20 can be the same inFIGS. 2A and 2B.

An upper surface 20 a of the anti-reflection layer 20 opposite the IDTelectrode 12 can be relatively flat in the surface acoustic wave device2. A surface roughness of the upper surface 20 a of the anti-reflectionlayer 20 can be about 3.5 nm. In some embodiments, the roughness of theupper surface 20 a can be in a range from, for example, 3 nm to 4 nm. Insome embodiments, the roughness of the upper surface 20 a can be lessthan, for example, 4.5 nm. The smoother and/or flatter surface of uppersurface 20 a of the anti-reflection layer 20 opposite the IDT electrode12 relative to the upper surface 14 a′ of the anti-reflection layer 14′of FIG. 1B can result in less variation in resistance and lesselectrical degradation in a filter.

The piezoelectric layer 10 may include any suitable piezoelectricmaterial, such as a lithium niobate (LN) layer or a lithium tantalate(LT) layer. A thickness tl of the piezoelectric layer 10 can be selectedbased on a wavelength λ or L of a surface acoustic wave generated by thesurface acoustic wave resonator 2 in certain applications. The IDTelectrode 12 has a pitch that sets the wavelength λ or L of a surfaceacoustic wave generated by the surface acoustic wave device 2. Thepiezoelectric layer 10 can be sufficiently thick to avoid significantfrequency variation.

The IDT electrode 12 can be an aluminum (Al) IDT electrode. The IDTelectrode 12 may include any other suitable IDT material. For example,the IDT electrode 12 may include copper (Cu), magnesium (Mg), titanium(Ti), etc. The IDT electrode 12 may include alloys, such as AlMgCu,AlCu, etc. The IDT electrode 12 can include a conductive layer that hasa reflectivity of at least 0.3 for light having a wavelength of 365nanometers. The IDT electrode 12 can include a conductive layer that hasa reflectivity of at least 0.5 for light having a wavelength of 365nanometers. The IDT electrode 12 can include a conductive layer that hasa reflectivity of at least 0.75 for light having a wavelength of 365nanometers. As shown in FIG. 7, the IDT electrode can be a multi-layerIDT in certain embodiments.

The IDT electrode 12 has a thickness t2. In some embodiments, thethickness t2 of the IDT electrode 12 can be about 0.05 L. For example,when the wavelength L is 4 μm, the thickness t2 can be 200 nm. Unlikethe embodiment illustrated in FIG. 1B, the original thickness and thefinal thickness of the IDT electrode 12 can be the same or very similarin the embodiment in FIGS. 2A and 2B. The thickness t5 of theanti-reflection layer 20 can be in a range from, for example, 0.004 L to0.06 L or 8 nm to 240 nm. The thickness t2 of the IDT electrode 12 canbe about 0.05 L. For example, when the wavelength L is 4 μm, thethickness t2 can be 200 nm.

The anti-reflection layer 20 can have a thickness t5. The thickness t5can vary for different materials used for the anti-reflection layer 20.Also, the determination of the thickness t5 can be based at least inpart on reflectivity of the anti-reflection layer 20 and/or line widths,for instance, as explained below with respect to FIGS. 4A to 6. Forexample, when the anti-reflection layer 20 is an amorphous siliconlayer, the thickness t5 can be about 9 nm (e.g., 0.00225 L when thewavelength L is 4 μm), which can give a reflectivity of 0.07 in someembodiments. For example, when the anti-reflection layer 20 is a siliconoxynitride layer, the thickness t5 can be about 110 nm, which can give areflectivity of 0.17 in some embodiments.

The temperature compensation layer 18 can include any suitable material.For example, the temperature compensation layer 18 can be a silicondioxide (SiO₂) layer. The temperature compensation layer 18 can be alayer of any other suitable material having a positive temperaturecoefficient of frequency. For instance, the temperature compensationlayer 18 can be a tellurium dioxide (TeO₂) layer or a siliconoxyfluoride (SiOF) layer in certain applications. A temperaturecompensation layer can include any suitable combination of SiO₂, TeO₂,and/or SiOF.

The temperature compensation layer 18 can bring the temperaturecoefficient of frequency (TCF) of the SAW resonator 2 closer to zerorelative to a similar SAW resonator without the temperature compensationlayer 18. The temperature compensation layer 18 together with a lithiumniobate piezoelectric layer can improve the electromechanical couplingcoefficient (k²) of the SAW resonator 2 relative to a similar SAWresonator with a lithium tantalate piezoelectric layer and without thetemperature compensation layer 18. Improved k² of the temperaturecompensation layer 18 can be more pronounced when the SAW resonator 2includes a lithium niobate layer as the piezoelectric layer 10. Incertain embodiments, for example, as illustrated in FIGS. 8B and 8C, thetemperature compensation layer 18 may be omitted.

The temperature compensation layer 18 has a thickness t4. In someembodiments, the thickness t4 of the temperature compensation layer 18can be in a range from 0.1 L to 0.5 L. For example, when the wavelengthL is 4 μm, the thickness t4 of the temperature compensation layer 14 canbe 1200 nm.

FIG. 3A is a graph of a reference wiring resistance measurement and awiring resistance measurement of the SAW resonator 1 illustrated in FIG.1B. A wiring resistance can be measured using a resistance wire test. Awiring resistance can also be referred to as an IDT resistance orelectrode resistance. The reference wiring resistance can be a wiringresistance of a SAW resonator that does not include an anti-reflectivematerial over an IDT electrode. The wiring resistance of the SAWresonator 1 is about 1.09 (e.g., 9% increase from the reference wiringresistance). This can result from the compound layer 14′ degrading theperformance of the SAW resonator 1 as compared to the reference SAWresonator that does not include the anti-reflective material.

FIG. 3B is a graph of a reference wiring resistance measurement and awiring resistance measurement of the SAW resonator 2 illustrated in FIG.2B. The wiring resistance of the SAW resonator 2 is substantially thesame or very similar to the reference wiring resistance. In other words,the anti-reflection layer 20 does not noticeably degrade the wiringresistance of the SAW resonator 2 as compared to the reference SAWresonator. Therefore, the SAW resonator 2 illustrated in FIG. 2B may bea more desirable than the SAW resonator 1 illustrated in FIG. 1B incertain applications. The anti-reflection film 20 of the surfaceacoustic wave resonator 2 of FIG. 2B can contribute less than 2% ofwiring resistance.

FIG. 4A is a graph of ellipsometer measurement results of reflectivityof an epoxy resin layer, a silicon oxynitride (SiON) layer, and anamorphous silicon (a-Si) layer for various thicknesses at a wavelengthof 365 nm. These layers were deposited on a silicon substrate and thenreflectivity was measured. The graph indicates that the thickness ofthese anti-reflection layers impacts reflectivity. A reflectivity of 1can mean that 100% of light emitted from a light source is reflectedback. A reflectivity of 0 can mean that 0% of the light emitted from thelight source is reflected. A first measurement result 30 is a result ofreflectivity of the epoxy resin layer. A second measurement result 32 isa result of the SiON layer. A third measurement result 34 is a result ofthe a-Si layer. The first result 30 shows that the reflectivity isbetween about 0.1 and about 0.15 for thicknesses of the epoxy resinlayer larger than about 50 nm.

FIG. 4B is a table with the lowest reflectivity values of the second andthird results 32 and 34, respectively, of FIG. 4A. The second result 32indicates that the lowest reflectivity can be obtained when the SiONlayer has a thickness of about 110 nm. The third result 34 indicatesthat the lowest reflectivity can be obtained when the a-Si layer has athickness of about 9 nm. The reflectivity of the anti-reflection layercan depend on a combination of a material of the anti-reflection layerand a thickness of the anti-reflection layer. The thickness of theanti-reflection layer can be selected to achieve a reflectivity that isno greater than a threshold value. For instance, the thickness of theanti-reflection layer can be selected such that the reflectivity is 0.2or less for a given material of the anti-reflection layer. FIG. 4Aindicates that a reflectivity of less than about 0.2 can be obtainedwith an amorphous silicon anti-reflection layer with a thickness in arange from about 5 nm to about 15 nm. FIG. 4A indicates that areflectivity of less than about 0.2 can be obtained with an siliconoxynitride anti-reflection layer with a thickness in a range from about105 nm to about 115 nm.

FIG. 5A is a graph of measurement results of line widths for differentresist thicknesses of a resist film of a SAW resonator structure used ina lithography process. The SAW resonator structure used in thesimulation of FIG. 5A does not include an anti-reflection layer betweenits IDT electrode and the resist film. A line width range rl from abottom side to a top side of the measurement curve can be observed fromthis graph. The line width range r1 of the measurement results of FIG.5A is about 0.15 nm.

FIG. 5B is a graph of measurement results of line widths for differentresist thicknesses of a resist film of a SAW resonator structure used ina lithography process. The SAW resonator structure used in themeasurement of FIG. 5B includes an epoxy resin layer between its IDTelectrode and the resist film. A line width range r2 from a bottom sideto a top side of the measurement curve can be observed from this graph.The line width range r2 of the measurement results of FIG. 5B is about0.05 nm.

FIG. 5C is a graph of measurement results of line width values fordifferent resist thicknesses of a resist film of a SAW resonatorstructure according to an embodiment used in a lithography process. TheSAW resonator structure used in the measurement of FIG. 5C includes anamorphous silicon (a-Si) layer between its IDT electrode and the resistfilm. A line width range r3 from a bottom side to a top side of themeasurement curve can be observed from this graph. The line width ranger3 of the measurement results of FIG. 5C is about 0.05 nm.

FIG. 5D is a graph of measurement results of line width values fordifferent resist thicknesses of a resist film of a SAW resonatorstructure according to an embodiment used in a lithography process. TheSAW resonator structure used in the measurement of FIG. 5D includes asilicon oxynitride (SiON) layer between its IDT electrode and the resistfilm. A line width range r4 from a bottom side to a top side of themeasurement curve can be observed from this graph. The line width ranger4 of the measurement results of FIG. 5D is about 0.1 nm.

FIG. 6 is a graph of fit curves (also referred to as swing curves) ofdata points at the bottom sides of the measurement results curvesillustrated in FIGS. 5A-5D. The graph shows normalized line width innanometer on y-axis and normalized resist thickness in nanometer onx-axis. These results may be used in determining the thickness t5 of theanti-reflection layer 20 of FIGS. 2A and 2B that meets a desiredspecification.

For example, a specification for a SAW resonator may specify a resistthickness variation to be within 1% (e.g., +/−1% or a total variation of2%), a frequency shift to be below 1 megahertz (MHz) at a frequency of 2gigahertz (GHz), and a frequency shift sensitivity to be 0.85 MHz/nm.This specification can be for a Band 25 filter. In such specification,at a frequency (f) of 2 GHz and velocity (V) of 4000 m/s, line width canbe calculated to be 0.5 μm. Also, to satisfy such specification, theline width distribution should be lower than about 1.18 nm (1 MHzfrequency shift/0.85 MHz/nm frequency shift sensitivity), which is about0.236% of the line width. Accordingly, with a line width distribution of0.2% or less, stringent SAW resonator specifications can be met.

FIG. 7 illustrates a cross section of a surface acoustic wave resonator3 according to an embodiment. The illustrated SAW resonator 3 includes apiezoelectric layer 10, an interdigital transducer (IDT) electrode 12′over the piezoelectric layer 10, an anti-reflection layer 20 over theIDT electrode 12′, and a temperature compensation layer 18 over theanti-reflection layer 20. The SAW resonator 3 illustrated in FIG. 7 isgenerally similar to the SAW resonator 2 illustrated in FIG. 2B.However, unlike the SAW resonator 2, the IDT electrode 12′ of the SAWresonator 3 is a multi-layer IDT electrode (e.g., includes two layers).As illustrated, the IDT electrode 12′ includes an upper layer 24 and alower layer 22 positioned between the upper layer 24 and thepiezoelectric layer 10. The upper layer 24 can be an aluminum layer. Thelower layer 22 can be a molybdenum layer, a tungsten layer, a goldlayer, a tantalum layer, a platinum layer, a silver layer, or aruthenium layer, for example. SAW resonators can include a multi-layerIDT electrode that includes three or more layers in some otherembodiments. Any suitable principles and advantages disclosed herein canbe applied to single layer IDT electrodes or multi-layer IDT electrodesthat include two or more IDT layers.

FIG. 8A illustrates a cross section of a surface acoustic wave resonator4 according to an embodiment. The illustrated SAW resonator 4 includes asupport layer 26, a piezoelectric layer 10 over the support layer 26, anIDT electrode 12 over the piezoelectric layer 10, an anti-reflectionlayer 20 over the IDT electrode 12, and a temperature compensation layer18 over the anti-reflection layer 20. FIG. 8A illustrates that theanti-reflection layers disclosed herein can be implemented in acousticwave resonators that include multi-layer piezoelectric substrates. TheSAW resonator 4 illustrated in FIG. 8A is generally similar to the SAWresonator 2 illustrated in FIG. 2B. However, unlike the SAW resonator 2,the SAW resonator 4 includes the support layer 26. By including thesupport layer 26, higher order spurious modes can be suppressed. In someembodiments, the support layer 26 can have a relatively high acousticimpedance. An acoustic impedance of the support layer 26 can be higherthat ac acoustic impedance of the piezoelectric layer 10. The supportlayer 26 can be a silicon layer, a spinel layer, a magnesium oxidespinel layer, a quartz layer, a ceramic layer, a glass layer, a sapphirelayer, a silicon nitride layer, an aluminum nitride layer, a diamondlayer such as synthetic diamond layer, or the like. In some otherembodiments (not illustrated), one or more additional layer can beincluded between the substrate layer and the piezoelectric layer. Theone or more additional layers can include a silicon dioxide layer or asilicon nitride layer, for example.

FIG. 8B illustrates a cross section of a surface acoustic wave resonator5 according to an embodiment. The illustrated SAW resonator 5 includes apiezoelectric layer 10, an IDT electrode 12 over the piezoelectric layer10, and an anti-reflection layer 20 over the IDT electrode 12. Thesurface acoustic wave resonator 5 is like the surface acoustic waveresonator 2 of FIG. 2B, except that the SAW resonator 5 does not includethe temperature compensation layer 18. In certain embodiments, a lithiumtantalate layer may be a more suitable piezoelectric material than thelithium niobate layer when there is no temperature compensation layerpresent in the SAW resonator. A SAW resonator without a temperaturecompensation layer over an IDT electrode can include a multi-layer IDTelectrode in certain instances. Alternatively or additionally, a SAWresonator without a temperature compensation layer over the IDTelectrode can include a multi-layer piezoelectric substrate.

FIG. 8C illustrates another cross section of the surface acoustic waveresonator 5 illustrated in FIG. 8B. The illustrated SAW resonator 5includes the piezoelectric layer 10, the IDT electrode 12 over thepiezoelectric layer 10, the anti-reflection layer 20 over the IDTelectrode 12. The IDT electrode 12 includes a first IDT electrode finger12x extending from a first bus bar (not shown) and a second IDT finger12y extending from a second bus bar (not shown). The first IDT electrodefinger 12x and the second IDT electrode finger 12y are spaced apart fromeach other by a gap 36. The gap 36 can be free from the anti-reflectionlayer 20. The portion of the piezoelectric layer 10 under the gap 36 isfree from the anti-reflection layer 20.

In some embodiments, the anti-reflection layer 20 can be patterned suchthat the anti-reflection layer 20 substantially covers an upper surfaceof IDT fingers of the IDT electrode 12. A width W1 of theanti-reflection layer 20 over IDT electrode finger 12x and a width W2 ofthe IDT electrode finger 12x can be generally similar. In someembodiments the width W1 of the anti-reflection layer 20 over the IDTelectrode finger 12x can be the same as or shorter than the width W2 ofthe IDT electrode finger 12x. In some embodiments, a side wall 12 b ofthe IDT electrode finger 12x that extends from a lower surface of theIDT electrode finger 12x to the upper surface of the IDT electrodefinger 12x, can be perpendicular with an upper surface of thepiezoelectric layer 10, or tapered. The side wall 12 b of the IDTelectrode finger 12x can be free from the anti-reflection layer 20. Theanti-reflection layer 20 can have a footprint that corresponds to afootprint of IDT electrode fingers of the IDT electrode 12 in theacoustically active part of the SAW resonator 5. The SAW resonator 5and/or any other SAW resonators disclosed herein can include part of theanti-reflection layer 20 over a bus bar of the IDT electrode 12. In someother embodiments, a bus bar can be free from the anti-reflection layer20. In some other embodiments, a bus bar can partly covered by theanti-reflection layer 20 and partly free from the anti-reflection layer20.

FIG. 9A illustrates a cross section of a Lamb wave device 7 according toan embodiment. The Lamb wave device 7 can be a Lamb wave resonator. TheLamb wave device 7 includes a piezoelectric layer 10, an IDT electrode12 over the piezoelectric layer 10, an anti-reflection layer 20 over theIDT electrode 12, and a temperature compensation layer 18 over thepiezoelectric layer 10. The Lamb wave device 7 also includes a substrate35, and an air cavity 37 between the piezoelectric layer 10 and thesubstrate 35. The substrate 35 can include any suitable material. Forexample, the substrate 35 can be a semiconductor substrate, such as asilicon substrate. As illustrated, the Lamb wave device 7 includes partof the anti-reflection layer 20 over a bus bar of the IDT electrode 12.In some other embodiments (not illustrated), a bus bar can be free fromthe anti-reflection layer. In some other embodiments (not illustrated),a bus bar can partly covered by the anti-reflection layer and partlyfree from the anti-reflection layer.

FIG. 9B illustrates a cross section of a Lamb wave device 8 according toanother embodiment. The Lamb wave device 8 can be a Lamb wave resonator.The Lamb wave device 8 is like the Lamb wave device 7 of FIG. 9A exceptthat the Lamb wave device 8 includes a solid acoustic mirror 29 and asubstrate 41 in place of the substrate 35 and the cavity 37. The solidacoustic mirror 29 can include acoustic Bragg reflectors. For instance,the solid acoustic mirror 29 can include alternating layers of a lowimpedance layer 29 a and a high impedance layer 29 b. As one example,the low impedance layer 29 a can be a silicon dioxide layer and the highimpedance layer 29 b can be a tungsten layer. As another example, thelow impedance layer 29 a can be a silicon dioxide layer and the highimpedance layer 29 b can be a molybdenum layer. The substrate 41 caninclude any suitable material. For example, the substrate 41 can be asemiconductor substrate, such as a silicon substrate.

A method of manufacturing an acoustic wave device according to anembodiment will now be described. The method can include providing apiezoelectric layer and forming (e.g., depositing) an interdigitaltransducer electrode material over the piezoelectric layer. Theinterdigital transducer electrode material can include aluminum. Themethod can include forming (e.g., depositing) an anti-reflection layerover the interdigital transducer electrode material. The anti-reflectionmaterial can remain distinct from the interdigital transducer materialafter a heating process. The anti-reflection material can reducereflections from the interdigital transducer material duringphotolithography. The method can include forming (e.g., depositing) aresist film over the anti-reflection layer. The resist film can bepatterned, for example, by a stepper. The method can include patterning(e.g., etching) the interdigital transducer electrode material to forman interdigital transducer electrode. The method can include removingthe resist film. The method can include forming (e.g., depositing) atemperature compensation layer over at least a portion of thepiezoelectric layer, the interdigital transducer electrode, and/or theanti-reflection layer.

A SAW device including any suitable combination of features disclosedherein be included in a filter arranged to filter a radio frequencysignal in a fifth generation (5G) New Radio (NR) operating band withinFrequency Range 1 (FR1). A filter arranged to filter a radio frequencysignal in a 5G NR operating band can include one or more SAW devicesdisclosed herein. FR1 can be from 410 MHz to 7.125 GHz, for example, asspecified in a current 5G NR specification. One or more SAW devices inaccordance with any suitable principles and advantages disclosed hereincan be included in a filter arranged to filter a radio frequency signalin a 4G LTE operating band and/or in a filter having a passband thatincludes a fourth generation (4G) Long Term Evolution (LTE) operatingband and a 5G NR operating band.

Acoustic wave devices disclosed herein can be implemented in astandalone filter. Acoustic wave devices disclosed herein can beimplemented in one or more filters of multiplexer (e.g., a duplexer)with fixed multiplexing. Acoustic wave devices disclosed herein can beimplemented in one or more filters of multiplexer with switchedmultiplexing. Acoustic wave devices disclosed herein can be implementedin one or more filters of a multiplexer with a combination of fixedmultiplexing and switched multiplexing.

FIG. 10A is a schematic diagram of an example transmit filter 45 thatincludes surface acoustic wave resonators of a surface acoustic wavecomponent according to an embodiment. The transmit filter 45 can be aband pass filter. The illustrated transmit filter 45 is arranged tofilter a radio frequency signal received at a transmit port TX andprovide a filtered output signal to an antenna port ANT. The transmitfilter 45 includes series SAW resonators TS1, TS2, TS3, TS4, TS5, TS6,and TS7, shunt SAW resonators TP1, TP2, TP3, TP4, and TP5, series inputinductor L1, and shunt inductor L2. Some or all of the SAW resonatorsTS1, TS2, TS3, TS4, TS5, TS6, and TS7 and/or TP1, TP2, TP3, TP4, and TP5can be a SAW resonators with an anti-reflection layer in accordance withany suitable principles and advantages disclosed herein. For instance,one or more of the SAW resonators of the transmit filter 45 can be asurface acoustic wave resonator 2 of FIG. 2B. Alternatively oradditionally, one or more of the SAW resonators of the transmit filter45 can be any surface acoustic wave resonators disclosed herein (e.g., asurface acoustic wave resonator 3 of FIG. 7, a surface acoustic waveresonator 4 of FIG. 8A, or a surface acoustic wave resonator 5 of FIGS.8B and 8C). Any suitable number of series SAW resonators and shunt SAWresonators can be included in a transmit filter 45.

FIG. 10B is a schematic diagram of a receive filter 50 that includessurface acoustic wave resonators of a surface acoustic wave componentaccording to an embodiment. The receive filter 50 can be a band passfilter. The illustrated receive filter 50 is arranged to filter a radiofrequency signal received at an antenna port ANT and provide a filteredoutput signal to a receive port RX. The receive filter 50 includesseries SAW resonators RS1, RS2, RS3, RS4, RS5, RS6, RS7, and RS7, shuntSAW resonators RP1, RP2, RP3, RP4, and RPS, and RP6, shunt inductor L2,and series output inductor L3.Some or all of the SAW resonators RS1,RS2, RS3, RS4, RS5, RS6, RS7, and RS8 and/or RP1, RP2, RP3, RP4, RPS,and RP6 can be SAW resonators with an anti-reflection layer inaccordance with any suitable principles and advantages disclosed herein.For instance, one or more of the SAW resonators of the receive filter 50can be a surface acoustic wave resonator 2 of FIG. 2B. Alternatively oradditionally, one or more of the SAW resonators of the receive filter 50can be any surface acoustic wave resonator disclosed herein (e.g., asurface acoustic wave resonator 3 of FIG. 7, a surface acoustic waveresonator 4 of FIG. 8A, or a surface acoustic wave resonator 5 of FIGS.8B and 8C). Any suitable number of series SAW resonators and shunt SAWresonators can be included in a receive filter 50.

FIG. 11 is a schematic diagram of a radio frequency module 75 thatincludes a surface acoustic wave component 76 according to anembodiment. The illustrated radio frequency module 75 includes the SAWcomponent 76 and other circuitry 77. The SAW component 76 can includeone or more SAW resonators with any suitable combination of features ofthe SAW resonators and/or acoustic wave devices disclosed herein. TheSAW component 76 can include a SAW die that includes SAW resonators.

The SAW component 76 shown in FIG. 11 includes a filter 78 and terminals79A and 79B. The filter 78 includes SAW resonators. One or more of theSAW resonators can be implemented in accordance with any suitableprinciples and advantages of the surface acoustic wave resonator 2 ofFIG. 2B and/or any surface acoustic wave resonator disclosed herein. Thefilter 78 can be a TC-SAW filter arranged as a band pass filter tofilter radio frequency signals with frequencies below about 3.5 GHz incertain applications. The terminals 79A and 78B can serve, for example,as an input contact and an output contact. The SAW component 76 and theother circuitry 77 are on a common packaging substrate 80 in FIG. 11.The package substrate 80 can be a laminate substrate. The terminals 79Aand 79B can be electrically connected to contacts 81A and 81B,respectively, on the packaging substrate 80 by way of electricalconnectors 82A and 82B, respectively. The electrical connectors 82A and82B can be bumps or wire bonds, for example. The other circuitry 77 caninclude any suitable additional circuitry. For example, the othercircuitry can include one or more one or more power amplifiers, one ormore radio frequency switches, one or more additional filters, one ormore low noise amplifiers, the like, or any suitable combinationthereof. The radio frequency module 75 can include one or more packagingstructures to, for example, provide protection and/or facilitate easierhandling of the radio frequency module 75. Such a packaging structurecan include an overmold structure formed over the packaging substrate75. The overmold structure can encapsulate some or all of the componentsof the radio frequency module 75.

FIG. 12 is a schematic diagram of a radio frequency module 84 thatincludes a surface acoustic wave component according to an embodiment.As illustrated, the radio frequency module 84 includes duplexers 85A to85N that include respective transmit filters 86A1 to 86N1 and respectivereceive filters 86A2 to 86N2, a power amplifier 87, a select switch 88,and an antenna switch 89. The radio frequency module 84 can include apackage that encloses the illustrated elements. The illustrated elementscan be disposed on a common packaging substrate 80. The packagingsubstrate can be a laminate substrate, for example.

The duplexers 85A to 85N can each include two acoustic wave filterscoupled to a common node. The two acoustic wave filters can be atransmit filter and a receive filter. As illustrated, the transmitfilter and the receive filter can each be band pass filters arranged tofilter a radio frequency signal. One or more of the transmit filters86A1 to 86N1 can include one or more SAW resonators in accordance withany suitable principles and advantages disclosed herein. Similarly, oneor more of the receive filters 86A2 to 86N2 can include one or more SAWresonators in accordance with any suitable principles and advantagesdisclosed herein. Although FIG. 12 illustrates duplexers, any suitableprinciples and advantages disclosed herein can be implemented in othermultiplexers (e.g., quadplexers, hexaplexers, octoplexers, etc.) and/orin switch-plexers.

The power amplifier 87 can amplify a radio frequency signal. Theillustrated switch 88 is a multi-throw radio frequency switch. Theswitch 88 can electrically couple an output of the power amplifier 87 toa selected transmit filter of the transmit filters 86A1 to 86N1. In someinstances, the switch 88 can electrically connect the output of thepower amplifier 87 to more than one of the transmit filters 86A1 to86N1. The antenna switch 89 can selectively couple a signal from one ormore of the duplexers 85A to 85N to an antenna port ANT. The duplexers85A to 85N can be associated with different frequency bands and/ordifferent modes of operation (e.g., different power modes, differentsignaling modes, etc.).

FIG. 13A is a schematic block diagram of a module 90 that includes apower amplifier 92, a radio frequency switch 93, and duplexers 91A to91N in accordance with one or more embodiments. The power amplifier 92can amplify a radio frequency signal. The radio frequency switch 93 canbe a multi-throw radio frequency switch. The radio frequency switch 93can electrically couple an output of the power amplifier 92 to aselected transmit filter of the duplexers 91A to 91N. One or morefilters of the duplexers 91A to 91N can include any suitable number ofsurface acoustic wave resonators with an anti-reflection layer inaccordance with any suitable principles and advantages discussed herein.Any suitable number of duplexers 91A to 91N can be implemented.

FIG. 13B is a schematic block diagram of a module 90′ that includesfilters 91A′ to 91N′, a radio frequency switch 93′, and a low noiseamplifier 96 according to an embodiment. One or more filters of thefilters 91A′ to 91N′ can include any suitable number of acoustic waveresonators in accordance with any suitable principles and advantagesdisclosed herein. Any suitable number of filters 91A′ to 91N′ can beimplemented. The illustrated filters 91A′ to 91N′ are receive filters.In some embodiments (not illustrated), one or more of the filters 91A′to 91N′ can be included in a multiplexer that also includes a transmitfilter. The radio frequency switch 93′ can be a multi-throw radiofrequency switch. The radio frequency switch 93′ can electrically couplean output of a selected filter of filters 91A′ to 91N′ to the low noiseamplifier 96. In some embodiments (not illustrated), a plurality of lownoise amplifiers can be implemented. The module 90′ can includediversity receive features in certain applications.

FIG. 14 is a schematic block diagram of a module 95 that includesduplexers 91A to 91N and an antenna switch 94. One or more filters ofthe duplexers 91A to 91N can include any suitable number of surfaceacoustic wave resonators with an anti-reflection layer in accordancewith any suitable principles and advantages discussed herein. Anysuitable number of duplexers 91A to 91N can be implemented. The antennaswitch 94 can have a number of throws corresponding to the number ofduplexers 91A to 91N. The antenna switch 94 can electrically couple aselected duplexer to an antenna port of the module 95.

FIG. 15A is a schematic diagram of a wireless communication device 100that includes filters 103 in a radio frequency front end 102 accordingto an embodiment. The filters 103 can include one or more SAW resonatorsin accordance with any suitable principles and advantages discussedherein. The wireless communication device 100 can be any suitablewireless communication device. For instance, a wireless communicationdevice 100 can be a mobile phone, such as a smart phone. As illustrated,the wireless communication device 100 includes an antenna 101, an RFfront end 102, a transceiver 104, a processor 105, a memory 105, and auser interface 107. The antenna 101 can transmit RF signals provided bythe RF front end 102. Such RF signals can include carrier aggregationsignals. Although not illustrated, the wireless communication device 90can include a microphone and a speaker in certain applications.

The RF front end 102 can include one or more power amplifiers, one ormore low noise amplifiers, one or more RF switches, one or more receivefilters, one or more transmit filters, one or more duplex filters, oneor more multiplexers, one or more frequency multiplexing circuits, thelike, or any suitable combination thereof. The RF front end 102 cantransmit and receive RF signals associated with any suitablecommunication standards. The filters 103 can include SAW resonators of aSAW component that includes any suitable combination of featuresdiscussed with reference to any embodiments discussed above.

The transceiver 104 can provide RF signals to the RF front end 102 foramplification and/or other processing. The transceiver 104 can alsoprocess an RF signal provided by a low noise amplifier of the RF frontend 102. The transceiver 104 is in communication with the processor 105.The processor 105 can be a baseband processor. The processor 105 canprovide any suitable base band processing functions for the wirelesscommunication device 100. The memory 106 can be accessed by theprocessor 105. The memory 106 can store any suitable data for thewireless communication device 100. The user interface 107 can be anysuitable user interface, such as a display with touch screencapabilities.

FIG. 15B is a schematic diagram of a wireless communication device 110that includes filters 103 in a radio frequency front end 102 and secondfilters 113 in a diversity receive module 112. The wirelesscommunication device 110 is like the wireless communication device 100of FIG. 15A, except that the wireless communication device 120 alsoincludes diversity receive features. As illustrated in FIG. 15B, thewireless communication device 120 includes a diversity antenna 111, adiversity module 112 configured to process signals received by thediversity antenna 111 and including filters 113, and a transceiver 104in communication with both the radio frequency front end 102 and thediversity receive module 112. The filters 113 can include one or moreSAW resonators that include any suitable combination of featuresdiscussed with reference to any embodiments discussed above.

Although embodiments disclosed herein relate to surface acoustic waveresonators, any suitable principles and advantages disclosed herein canbe applied to other types of acoustic wave resonators and/or acousticwave devices, such as Lamb wave resonators and/or boundary waveresonators. For example, any suitable combination of features of ananti-reflection layer over an IDT electrode disclosed herein can beapplied to a Lamb wave resonator and/or a boundary wave resonator.

Any of the embodiments described above can be implemented in associationwith mobile devices such as cellular handsets. The principles andadvantages of the embodiments can be used for any systems or apparatus,such as any uplink wireless communication device, that could benefitfrom any of the embodiments described herein. The teachings herein areapplicable to a variety of systems. Although this disclosure includessome example embodiments, the teachings described herein can be appliedto a variety of structures. Any of the principles and advantagesdiscussed herein can be implemented in association with RF circuitsconfigured to process signals in a frequency range from about 30 kHz to300 GHz, such as in a frequency range from about 450 MHz to 8.5 GHz.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as die and/or acoustic wave components and/oracoustic wave filter assemblies and/or packaged radio frequency modules,uplink wireless communication devices, wireless communicationinfrastructure, electronic test equipment, etc. Examples of theelectronic devices can include, but are not limited to, a mobile phonesuch as a smart phone, a wearable computing device such as a smart watchor an ear piece, a telephone, a television, a computer monitor, acomputer, a modem, a hand-held computer, a laptop computer, a tabletcomputer, a personal digital assistant (PDA), a microwave, arefrigerator, an automobile, a stereo system, a DVD player, a CD player,a digital music player such as an MP3 player, a radio, a camcorder, acamera, a digital camera, a portable memory chip, a washer, a dryer, awasher/dryer, a copier, a facsimile machine, a scanner, amulti-functional peripheral device, a wrist watch, a clock, etc.Further, the electronic devices can include unfinished products.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,”“include,” “including” and the like are to be construed in an inclusivesense, as opposed to an exclusive or exhaustive sense; that is to say,in the sense of “including, but not limited to.” The word “coupled”, asgenerally used herein, refers to two or more elements that may be eitherdirectly connected, or connected by way of one or more intermediateelements. Likewise, the word “connected”, as generally used herein,refers to two or more elements that may be either directly connected, orconnected by way of one or more intermediate elements. Additionally, thewords “herein,” “above,” “below,” and words of similar import, when usedin this application, shall refer to this application as a whole and notto any particular portions of this application. Where the contextpermits, words in the above Detailed Description using the singular orplural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel apparatus, methods, andsystems described herein may be embodied in a variety of other forms;furthermore, various omissions, substitutions and changes in the form ofthe methods and systems described herein may be made without departingfrom the spirit of the disclosure. For example, while blocks arepresented in a given arrangement, alternative embodiments may performsimilar functionalities with different components and/or circuittopologies, and some blocks may be deleted, moved, added, subdivided,combined, and/or modified. Each of these blocks may be implemented in avariety of different ways. Any suitable combination of the elements andacts of the various embodiments described above can be combined toprovide further embodiments. The accompanying claims and theirequivalents are intended to cover such forms or modifications as wouldfall within the scope and spirit of the disclosure.

What is claimed is:
 1. An acoustic wave device comprising: apiezoelectric layer; an interdigital transducer electrode over thepiezoelectric layer, the interdigital transducer electrode including aconductive layer; an anti-reflection layer over the conductive layer,the anti-reflection layer including silicon; and a temperaturecompensation layer over the anti-reflection layer.
 2. The acoustic wavedevice of claim 1 wherein the anti-reflection layer is a siliconoxynitride layer.
 3. The acoustic wave device of claim 1 wherein theanti-reflection layer is an amorphous silicon layer.
 4. The acousticwave device of claim 1 wherein the anti-reflection layer includes amaterial and has a thickness that together cause reflectivity of theanti-reflection layer to be less than or equal to 0.2 for light having awavelength of 365 nanometers.
 5. The acoustic wave device of claim 1wherein the conductive layer is in physical contact with theanti-reflection layer.
 6. The acoustic wave device of claim 1 whereinthe conductive layer is an aluminum layer.
 7. The acoustic wave deviceof claim 1 further comprising a substrate layer, the piezoelectric layerbeing on the substrate layer.
 8. An acoustic wave device comprising: apiezoelectric layer; a interdigital transducer electrode over thepiezoelectric layer, the interdigital transducer electrode including afirst interdigital transducer electrode finger extending from a firstbus bar and a second interdigital transducer electrode finger extendingfrom a second bus bar, the first interdigital transducer electrodefinger and the second interdigital transducer finger being spaced apartfrom each other by a gap; and an anti-reflection layer over theinterdigital transducer electrode, the anti-reflection layer includingsilicon, the anti-reflection layer being free from material of theinterdigital transducer electrode, and the piezoelectric layer beingfree from the anti-reflection layer under the gap.
 9. The acoustic wavedevice of claim 8 further comprising a temperature compensation layerover the anti-reflection layer.
 10. The acoustic wave device of claim 8wherein the anti-reflection layer is an amorphous silicon layer having athickness in a range from 5 nanometers to 15 nanometers.
 11. Theacoustic wave device of claim 8 wherein the anti-reflection layer is asilicon oxynitride layer having a thickness in a range from 100nanometers to 120 nanometers.
 12. The acoustic wave device of claim 8wherein the interdigital transducer electrode includes an aluminumlayer, and the anti-reflection layer is in physical contact with thealuminum layer.
 13. The acoustic wave device of claim 12 wherein theanti-reflection layer has a reflectivity of 0.2 or less for light havinga wavelength of 365 nanometers.
 14. The acoustic wave device of claim 8further comprising a support substrate, the piezoelectric layer beingover the support substrate, and the support substrate having a higherimpedance than the piezoelectric layer.
 15. A method of manufacturing anacoustic wave device, the method comprising: providing an acoustic wavedevice structure with one or more interdigital transducer electrodelayers on a piezoelectric layer, the one or more interdigital transducerelectrode layers including a conductive layer; forming ananti-reflection layer over the conductive layer, the anti-reflectionlayer including silicon; and performing a photolithography processes topattern an interdigital transducer electrode from the one or moreinterdigital transducer electrode layers, the anti-reflection layerreducing reflection from the conductive layer during thephotolithography process.
 16. The method of claim 15 wherein theconductive layer includes aluminum.
 17. The method of claim 15 whereinthe anti-reflection layer has a reflectivity of 0.2 or less for lighthaving a wavelength of 365 nanometers.
 18. The method of claim 15wherein the conductive layer has a reflectivity of at least 0.5 forlight having a wavelength of 365 nanometers.
 19. The method of claim 15further comprising forming a temperature compensation layer over theanti-reflection layer.
 20. The method of claim 15 wherein theanti-reflection material remains distinct from the conductive layerafter a heating process